Recently there has been a trend in replacing conventional incandescent light bulbs with light emitting diodes (LEDs). LEDs are advantageous over conventional incandescent bulbs because they are more efficient in terms of energy use and longevity. Further, an increasing variety of lighting applications require precisely controlled spectral characteristics of the radiant energy (e.g., light).
However, the process of manufacturing light sources, such as LEDs, can be highly variable. LEDs are subject to manufacturing deviations, which result in each LED possessing slightly different light qualities despite originating from the same production run. LEDs designed to be of the same wavelength are often manufactured with slightly different wavelengths. This variability makes it difficult to achieve a desired spectral characteristic in a given environment (e.g., stage, broadcast studio, film set, photo shoot, architectural installations, retail displays, etc.), especially when multiple light fixtures having slightly different lighting qualities are being used. Further, there are many different manufacturers producing LEDs. Each manufacturer may have its own process and standards for constructing LEDs, which introduces additional variability. For example, a red LED made by a first manufacturer may have different lighting qualities compared to another red LED made by a second manufacturer. The variety in manufacturing processes and standards also makes it difficult for an end user using light fixtures from different manufacturers to achieve a desired spectral characteristic for a lighting application.
Some manufacturers even change the combination of LEDs that they use in their light fixtures, such that trying to reproduce the same, uniform color with multiple lighting fixtures can be a complex problem. For example, a first light fixture having a set of LEDs: x, y, z, may be driven by specific power components: a, b, c. A second light fixture having a set of LEDs: x′, y′, z′, may emit light of a different color if driven by the same power components: a, b, c.
Conventional lighting fixtures are also limited with respect to certain colors and color properties due to each fixture having a limited number of LEDs (i.e. 3 LEDs for red, green, and blue). This means that the available spectrum of colors which a conventional light fixture is capable of producing is limited and discrete.
Conventional light fixtures with LEDs also have drawbacks related to color shifting when dimming. Changes in electrical current through an LED affect the junction temperature of the device, which can shift the spectral power distributions. The lower energy (e.g., voltage, current) driving the LED causes a different radiant energy to be produced, thus causing a change in the wavelength of the light being emitted. This ruins the purity of the color produced and does not allow for a proper fade out or fade in of the colored light.
Thus, there exists a need in the art for a system and method of controlling one or more light fixtures with LEDs which have the capacity to address the above problems by driving the light fixture to consistently and uniformly emit light at a desired color.